The present invention relates to a detection device, a gyrosensor, and an electronic instrument.
A gyrosensor (physical quantity transducer) for detecting the physical quantity which changes due to external factors is incorporated in electronic instruments such as a digital camera, a video camera, a portable telephone, and a car navigation system. The gyrosensor detects the physical quantity such as the angular velocity and is used for image blur correction, position control, GPS autonomous navigation, and the like.
In recent years, a gyrosensor has been demanded which has a reduced weight and size and exhibits high detection accuracy. Therefore, a piezoelectric vibratory gyrosensor has attracted attention as one type of gyrosensor. In particular, a crystal piezoelectric vibratory gyrosensor using a crystal as the piezoelectric material is expected to be a sensor optimum for incorporation into many devices. The vibratory gyrosensor detects the physical quantity corresponding to the Coriolis force which occurs due to rotation (JP-A-6-160100).
In the vibratory gyrosensor, an output signal (output current) from a vibrator is very weak due to a reduction in weight and size of the vibrator. Therefore, a detection device which detects a desired signal (signal corresponding to the physical quantity such as the Coriolis force) based on such a weak output signal is required to have capability of detecting the desired signal with no distortion, low noise, and a gain as large as possible.
In the vibratory gyrosensor, the sensitivity is adjusted. The term “sensitivity” used herein refers to the amount of change (slope) in the output voltage of the vibratory gyrosensor (detection device) per unit angular velocity, for example. The sensitivity is adjusted so that the amount of change coincides with a reference value.
However, when providing a sensitivity adjustment circuit for adjusting the sensitivity, the sensitivity adjustment circuit increases noise such as flicker noise (1/f noise), whereby the S/N ratio deteriorates.